Control system



May 4, 1943. B. o. AUSTIN 2,318,043

CONTROL SYSTEM Filed July 12, 1941 INVENTOR 5min/f77 Huff/f7 Patented May 4, 1943 2,318,043 CONTROL SYSTEM Base-um o. Austin, rarest mus, Pa., signor u Westinghouse Electric a Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 12, 1941, Serial No. 402,169

13 Claims.

My invention relates, generally, to control systems and, more particularly, to systems for controlling the operation of Diesel or gas-electric buses.

Buses of the Diesel or gas-electric type are operated -by two pedals known as the accelereator pedal and the brake pedal. These pedals function in much the same manner as the control pedals on a standard automobile. Likewise, they re located in the same relative positions as in in automobile. However, there is no clutch oedal, since a mechanical clutch is not utilized in Diesel or ges-electric vehicles.

An object of my invention is to control the acceleration and the electric braking of a Diesel or gas-electric vehicle.

Another object of my invention is to automatically regulate the electric braking of a Diesel or gas-electric vehicle.

A further object of my invention is to automatically control the field excitation of the generator in a Diesel or gas-electric vehicle.

Still another object of my invention is to prevent current from circulating through the electrical equipment on a vehicle while it is standing with the air brakes applied.

A still further object oi' my invention is to prevent a Diesel or gas-electric vehicle from running backward on a grade by means of dynamic braking of the motor.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with my invention, the iield winding oi the motor of a Diesel or gas-electric vehicle is excited by the generator during electric braking. The braking current is regulated by a current responsive relay which controls the excitation of the generator. During acceleration the generator excitation is regulated by a voltage responsive relay which is also utilized to control the deenergization oi' the electrical equipment when the vehicle is brought to a standstill.

For a fuller understanding of the nature and objects of my invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing in which the single ilgure is a diagrammatic view of a control system embodying my invention.

Referring to the drawing, the system shown therein comprises an engine E for driving a generator G which supplies current to a motor M of a type suitable for propelling a vehicle (not shown). The generator G has an armature winding I and a tleld winding I I. The motor u ing dynamic braking. The ileld winding I3 of the motor M is energized by the generator G during dynamic braking.

The engine speed is regulated by controlling the generator excitation by means of a plurality of relays RI, R2, R3 and R4, responsive to the generator current, as fully described and claimed in the copending application of B. O. Austin and C. A. Atwell, Serial No. 315,374, led January 24, 1940. The relays RI, R2, R3 and R4 are set to operate in a predetermined sequence to vary the generator excitation by shunting portions of a. resistor I5 from the circuit for the field winding II, thereby controlling the load on the engine to regulate the engine speed.

A switch F is provided for connecting the eld winding II across the armature I0 of the generator G during acceleration of the vehicle. During dynamic braking of the vehicle the excitation for the generator G is provided from a. separate source, which may be a storage battery or other suitable source of direct current power.

A current regulating relay CR, which is of the vibrating type, is provided for regulating the excitation of the generator field winding II during dynamic braking. The relay CR is not utilized during acceleration, at which time the excitation of the generator is controlled by the relays RI, R2, R3 and R4, as hereinbefore described. The relay CR is provided with a current Winding I6 which is connected in the dynamic braking circuit for the motor M. 'I'he relay CR is also provided with a winding I'i which may be connected across the storage battery to change the setting of the relay CR, thereby varying the braking rate.

A braking controller BC, which may be of the drum type and pedal operated if desired, is provided for controlling the energization of the Winding Il of the relay CR and also the operation of the braking switch IB. An acceleration switch or controller AC, which may also be pedal operated and mechanically connected with an accelerator or throttle valve I8 for the engine E, co-

operates with the braking controller BC in the control of the switches P and E. The accelera.-

tion controller AC also controls the operation of the switch F for energizing the held winding of the generator G during acceleration of the vehicle. The controller BC may be so connected with the airbrake system for the vehicle that the aix-brakes operate in conjunction with the electrical braking in stopping the vehicle.

In order to make the generator voltage build up more rapidly during the early portion of the accelerating period, the eld windingl it is excited from the storage battery as well as being self excited from the generator. A voltage responsive relay VR is provided for automatically cutting oil the battery excitation when the generator attains a predetermined voltage and the battery excitation is no longer required. The relay VR. is provided with a coil l@ which is connected across the generator armature through the switch F and an interlock 2l on the switch P during the accelerating period. In this manner the relay VR is responsive to the generator voltage and may be utilized to control the generator excitation.

The relay VR is also provided with a coil 22 which is connected across the storage battery through interlocks 23 and 2 on the switches B and P, respectively. In this manner the relay VR may be utilized to control the operation of the switch B to prevent the generator from circulating current through the motor field and the generator armature while the bus is standing, as will be more fully described hereinafter.

.A key switch KS, which corresponds to the usual ignition switch on an automobile, is provided for disconnecting the storage battery from the control circuits when the vehicle is standing and the engine is not running. When the vehicle is standing with the engine idling with both the accelerator pedal and the brake pedal released and the key switch KS closed, the switch P is held closed, thereby connecting the generator G and motor M in a closed circuit for driving the vehicle. In the released position of the control pedals the actuating coil for the switch P is energized through a circuit which may be traced from B+ through conductors 2i and 2t, contact segment 2l on the controller BC, conductors 2t and 29, an interlock 3l on the switch B, conductor Si, the actuating coil of switch P, conductors 33 and 3d, and the switch KS to B+. In this manner, the switch P is normally held closed with both the accelerator pedal and the brake pedal released.

lin order to accelerate the vehicle, the accelerator pedal AC is depressed, thereby opening the throttle valve it and closing the contact members 3? and dit on the accelerator controller. The closing ci the contact member 35 establishes an energizing circuit for the actuating coil of the switch F which extends from conductor 2G through the contact member 35, conductor 3l, the actuating coil of the switch F, the conductors 33 and 3d, and the switch KS to B-. The closing of the switch F connects the generator eld winding il across the armature of the generator through a circuit which may be traced from one terminal of the generator G through conductors 26 and 3d, the switch F, conductor 39, the resistor t5, conductor di, the held winding il, conductor d2, contact members d3 and 3d of the relay CR, conductors @il and it and the coils of the relays R3, R2, Rd and Ri to the other terminal of the generator Cr.

The opening of the throttle l causes the engine E to increase its speed. The generator voltage increases and current ows from the generator armature through the engine speed relay coils Rl. R2, R3 and Ril through the switch P, the motor armature i2, and the series field winding i3 back to the generator G. In this manner voltage is gradually applied to the motor and the vehicle brought up to speed.

.As explained hereinbefore the generator is also excited from the battery to make the generator voltage build up more rapidly during the early portion of the accelerating period. The battery excitation circuit for the generator eld winding il may be traced from B+ through conductors 25 and 2b, the generator armature l, the relay coils Rl. Rl, R2 and RS, conductors tt and fie, the contact members it and it of the relay CR, conductor d2, the eld winding it, conductors it and dl, a resistor liti, conductor ld, an interlock 5i on the switch F, conductor 52, contact members 53 on the relay VR, conductors bil, and 3d and the switch KSto B-. As explained hereinbefore, the coil lil of the relay VR is connected across the generator armature. Therefore, when the generator voltage is increased to a predetermined value the relay VR operates to open the contact members 53, thereby cutting olif the battery excitation which is no longer required.

When the Vehicle attains the desired speed, the accelerator pedal is returned to the released position and the vehicle coasts until a braking edect is desired. As illustrated, the electric brake is controlled by the airbrake pedal. However, if desired, it could be arranged to be applied by returning the power pedal to the oi position.

While the Vehicle is coasting, the switch P is held closed, since its actuating coil is energized through the contact segment 2l of the braking controller BC. However, during coasting the switch Fv is open, since its actuating coil is deenergized by the opening of the contact members 35 of the accelerator control AC. Therefore, the eld winding il of the generator is not excited from the armature of the generator. Also, the interlock 5i on the switch F opens the battery excitation circuit for the field winding of the generator. Therefore, there is only residual excitation left in the generator and the engine is operating at idling speed since the throttle valve i123 is returned to the idling position by releasing the accelerator control AC.

The electric brake is applied by the iirst initial movement of the braking pedal, thereby opening the circuit through the contact segment 2l on the controller BC which deenergizes the actuating coil for the switch P causing this switch to open. The brakingswitch B is then closed as the result of the energization of its closing coil 55 through a circuit which may be traced from B+ through conductors 25 and 2E, interlock 2d on the switch P, conductor 56, contact members 5l on the relay VR., conductor 58, the closing coil 55 of the switch B, conductors 33 and 3G and the switch KS to B.

As explained hereinbefore, when the switch B is closed and the switch P is open the generator G excites the iield winding i3 of the motor M and thereby causes the motor to function as a generator and circulate current through the resistor it and the current coil of the regulating relay CR. The energy of the vehicle is dissipated in the resistor itl during braking and the braking current is regulated by the relay CR.

The field oi the generator is battery excited during braking, no self excitation being utilized. The battery excitation circuit may -be traced from B-I- through conductors 25 and 26, the generator armature, the relays RI, R4, R2 and R3, conductors 46 and 45, the contact members 44 and 43 of the relay CR, conductor 42, the field winding II, conductor 4I,contact members 6I and 62 of the relay CR, a resistor 63, conductor 64, an interlock 65 on the switch P, conductors 33 and 34 and switch KS to B-.

The relay CR regulates the generator excitation to maintain a predetermined current in the braking circuit. Therefore, the battery excitation is increased as the bus speed is reduced. When the vehicle speed -is sufllciently low full battery excitation is applied and the motor braking current begins to fade with a further decrease in the vehicle speed. The airbrake may then be applied to bring the vehicle to a complete stop. If desired, the airbrake may be applied simultaneously with the electric brake by manipulation of the brake pedal.

If the electric brake is applied while the engine is operating at a high idling speed there may be too much motor ileld excitation as a result of the high generator speed. In order to prevent an excessive motor voltage, the relay CR is provided with a set of back contacts which are momentarily closed to reverse the battery excitation of the generator iield in order to lower the excitation of the motor field until the engine speed is reduced to its normal idling speed. The foregoing condition may occur when rapid application of the electric brake is made just after removing the foot from the accelerating pedal and the engine speed has not had suiilcient time to reduce to the normal idling speed.

In order to prevent the generator from circulating current through the motor field and the generator armature while the vehicle is standing, the braking switch B is opened before the vehicle comes to a complete stop. This is accomplished by provi-ding a holding coil 66 on the switch B which is connected across the braking resistor I4 and is therefore energized by the voltage drop across this resistor. Thus the holding coil 66 will not hold the switch B closed when the generated volts of the motor approach zero or the vehicle speed is approaching zero. The energizing circuit for the coil l66 may be traced from one terminal of the resistor i4 through conductors 46 and 61, the coil 66, conductor 68, an interlock 69 on the switch F, conductor 1I, contact segment 12 on the controller BC, and conductor 13 to the other terminal of the resistor I4.

As explained hereinbefore, the closing coil 55 of the switch B is energized through contact members 51 of the relay VR. When the switch B closes the coil 22 of the relay VR is energized from the battery through a circuit which extends from B+ through conductors 25 and 26, the interlock 24 on the switch P, conductor 14, the interlock 23 on the switch B, conductors 15 and 16, the coil 22, conductors 11, 33 and 34, and the switch KS to B-. Accordingly, the relay VR opens its contact members 51 to deenergize the closing coil 55 of the switch B. However, the switch is held closed by the holding coil 66 until the vehicle speed is reduced so low that there is insufficient braking current to produce any braking effect.

If the brake is applied while the vehicle is standing, the switch B will close momentarily, since the contact member 51 on. the relay VR will be closed to establish an energizing circuit for the coil of switch B. However, the coil 22 of the lrelay VR is energized through the interlock 23 on the switch B, thereby operating the relay VR to deenergize the closing coil of the switch B. A contact member 16 on the relay VR shunts the interlock 23 on the switch B, thereby preventing the relay VR from being deenergized until the brake is released. As explained hereinbefore, the holding coil of the switch B will not hold the switch closed, since the motor is at zero speed and no voltage is applied to the holding coil. Therefore, no current is permitted to circulate through the generator and the motor eld while the vehicle is standing and the brake is applied.

The dynamic brake may be released at any vehicle speed by releasing the brake pedal, thereby opening the circuit through the contact segments 12 of the braking controller and deenergizing the holding coil 66 on the braking switch B. The switch P is closed by the energization of! its actuating coil through the contact segment 21 when the brake controller is in the released position.

Ihe switch P is kept closed at all times except when the brake is being utilized. In this manner the vehicle is prevented from running backward on grades so lon-g as the generator and motor circuits are in a motoring position. Any backward motion of the vehicle will cause the motor to brake dynamically through the generator, whether or not the generator is running.

The contact members 36 on the accelerator controller AC which shunt the contact segment 21 on the braking controller BC are for the purpose of preventing the switch P from opening when the accelerator pedal is depressed and the brake pedal depressed immediately afterwards. This permits power and brake to be applied at the same time which combination may be utilized on icy streets to prevent skidding of the vehicle.

If the brake pedal is pressed first, power will predominate if the accelerator pedal is pressed afterwards to close the switch F. The interlock 69 on th'e switch F releases the switch B and the interlock 3| on the switch B then causes the switch P to close. The vehicle will then be driven by the motor M while the airbrake is applied. In other words the power predominates under all conditions of operation so long as the accelerator pedal is depressed at any time.

As explained hereinbefore, the setting of the relay CR may be changed by energizing the coil I1 to vary the braking rate. The coil I1 is connected across the battery through a contact segment 19 on the braking controller BC. Thus, if a relatively low braking rate is desired the controller BC may be actuated to position I, in which position the coil I1 is energized and causes the relay CR to maintain a lower braking current. If maximum braking rate is desired, the controller BC may be actuated to position 2 in which position the coil I1 is not energized and more current is required in the series coil I6 on the relay CR to operate the relay. Accordingly, the relay regulates for a higher braking current, resulting in a higher braking rate.

As explained hereinbefore the relays RI, R2, R3 and R4 regulate the engine speed during motoring operation of the vehicle. During braking of the vehicle the engine operates at its idling speed.

From the foregoing description, it is apparent that I have provided a system for controlling 'both the acceleration and the electric braking of a self propelled vehicle such as a Diesel or gaselectric bus. Furthermore, 4the rate of electric `braking of the vehicle may be varied as desired by the operator.

Since many modifications may be made in the apparatus and arrangement of parts without departing from the spirit of my invention, l do not wish to be limited other than by the scope oi' the appended claims.

l claim as my invention:

1. In a control system, in combination, a motor having an armature winding and a eld winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for connecting the generator and the motor armature and :held winding in series-circuit relation for motoring operation, additional switching means for establishing dynamic braking connections for the motor, means for connecting said motor field winding for energization by the generator during dynamic braking, an engine accelerator controller, and a braking con= troller, said controllers cooperating in controlling the operation of said switching means.

2. ln a control system, in combination, a motor having an armature winding and a field winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for connecting the generator and the motor armature and eld winding in series-circuit rela tion for motoring operation, additional switching means for establishing dynamic braking connections for the motor, means for connecting said motor field winding for energization by the generator during dynamic braking, and independ= ently operable controllers for controlling the engine speed and electric braking, said controllers cooperating in controlling the operation of said switching means.

3. ln a control system, in combination, a motor for driving a vehicle, said motor having an armature Winding and a field winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for connecting the generator and the motor armature and field winding in series-circuit relation to propel the vehicle, additional switching means for establishing dynamic braking connections for the motor, means for connecting said. motor iield winding for energization lby the generator during dynamic braking, an engine accelerator controller, and a controller for controlling the vehicle braking, said controllers cooperating in con@ trolling the operation of said switching means.

4. n a control system, in combination, a motor for driving a vehicle, said motor having an armature winding and a iield winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for connecting the generator and the motor armature and field winding in series-circuit relation to propel the vehicle, additional switching means for establishing a dynamic braking circuit for the motor, means for connecting said motor iield winding for energization by the generator during dynamic braking, relay means responsive to the braking current for controlling the generator excitation during dynamic braking, a controller for controlling the operation of said switching means, and means associated with said controller for changing the calibration or said relay means.

5. In a control system, in combination, a motor for driving a vehicle, said motor having an armature winding and a field winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for con= necting the generator and the motor armature and eld winding in series-circuit relation to propel the vehicle, additional switching means for establishing a dynamic braking circuit for the motor, means for connecting said motor eld Winding for energization by the generator during dynamic braking, a relay lfor controlling the generator excitation during dynamic braking, said relay having an actuating coil connected in the dynamic braking circuit and a calibratlng coil, and separate means for energizing said calibrating coil.

6. In a control system, in combination, a motor for driving a vehicle, said motor having an armature winding and a field Winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for connecting the generator and the rnotor` armature and eld winding in series-circuit relation to prol the vehicle, additional switching means for establishing a dynamic braking circuit for the motor, means for connecting said motor ileld winding for energization by the generator during dynamic braking, a relay for controlling the generator excitation during dynamic braking, said relay having an actuating coil connected in the dynamic braking circuit and a calibrating coil, separate means for energizing said calibrating coil, and a braking controller rior controlling the energization of the Calibrating coil.

'7. in a control system, in combination, a motor for driving a vehicle, said motor having an armature winding and a field winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for connecting the generator and the motor armature and field winding in series-circuit relation to propel the vehicle, additional switching means for establishing a dynamic braking circuit for the motor, means for connecting said motor field winding for energization by the generator during dynamic braking, a relay for controlling the generator excitation during dynamic braking, said relay having an actuating coil connected in the dynamic braking circuit and a Calibrating coil, separate means for energizing said calibrating coil, and a braking controller for controlling the energization of the Calibrating coil, said braking controller also controlling the operation of the switching means for establishing the dynamic braking circuit for the motor.

8. ln a control system, in combination, a, motor for driving a vehicle, said motor having an armature winding and a eld winding, a generator for supplying current to the motor, an engine for driving the generator, switching means for connecting the generator and the motor armature and eld winding in series-circuit relation to propel the vehicle, additional switching means ror establishing a dynamic braking circuit for the motor, means for connecting said motor field winding for energization by the generator during dynamic braking, a relay for controlling the generator excitation during dynamic braking, said relay having an actuating coil connected in the dynamic braking circuit and a Calibrating coil, separate means for energizing said calibrating coil, a braking controller for controlling the energization of the calibrating coil, said braking controller also controlling the operation of the switching means for establishing the dynamic braking circuit for the motor, and an accelerating controller cooperating with the braking controller in controlling the operation of said switchlng meansD 9. In a control system, in combination, a motor for driving a vehicle, a generator for supplying current to the motor, said generator having an armature winding and a field winding, an engine for driving the generator, switching means for connecting the.generator armature and the motor in series-circuit relation to propel the vehicle,

`additional switching means for establishing dynamic braking connections for the motor, a switch for connecting the generator field winding across the generator armature, an additional source of excitation for the generator iield Winding, and a relay responsive to the generator voltage for connecting the generator iield winding to said additional source of excitation, said relay having an actuating coil connected across the generator armature through said switch.

10. In a control system, in combination, a motor for driving a vehicle, a generator for supplying current to the motor, said generator having an armature winding and a field winding, an engine for driving the generator, switching means for connecting the generator armature and the motor in series-circuit relation to propel the vehicle, additional switching means for establishing dynamic braking connections for the motor, a switch for connecting the generator eld winding across the generator armature, an additional source of excitation for the generator field winding, a relay responsive to the generator voltage for connecting the generator field winding to said additional source of excitation, said relay having an actuating coil vconnected across the generator armature through said switch, and an additional coil on said relay energized through said switching means.

il. In a control system, in combination, a motor for driving a vehicle, a generator for supplying current to the motor, said generator having an armature winding and a field Winding, an engine for driving the generator, switching means for connecting the generator armature and the motor in series-circuit relation to propel the vehicle, additional switching means for establishing dynamic braking connections for the motor, a switch for connecting the generator field winding across the generator armature, an additional source of excitation for the generator field winding, a relay responsive to the generator voltage for connecting the generator field winding to said additional source of excitation, said relay having an actuating coil connected across the generator armature through said switch, an additional coil on said relay energized throughsaid switching means,

and an accelerator controller and a. braking controller cooperating in the control of said switching means.

12. In a control system, in combination, a motor for driving a vehicle, a generator for supplying current to the motor, said generator having an armature winding and a lield winding, an engine for driving the generator, switching means for connecting the generator armature and the motor in series-circuit relation to propel the vehicle, additional switching means for establishing dynamic braking connections for the motor, a switch for connecting the generator field winding across the generator armature, an additional source of excitation for the generator eld winding, a relay responsive to the generator.voltage for connecting the generator field winding to said additional source of excitation, said relay having an actuating coil connected across the generator armature through said switch, and an additional coil on said relay energized through said switching means, an accelerator controller for controlling the operation of said switch, and a braking controller cooperating with said accelerator controller in the control of said switching means.

13. In a control system, in combination, a motor for driving a vehicle, a generator for supplying current to the motor, said generator having an armature winding and a field winding, an engine for driving the generator, switching means for connecting the generator armature and the motor in series-circuit relation to propel the vehicle, additional switching means for establishing dynamic braking connections for the motor, a switch' for connecting the generator eld winding across the generator armature, an additional source of excitation for the generator eld winding, a relay responsive to the generator voltage for connecting the generatoreld winding to said additional source of excitation, said relay having an actuating coil connected across the generator armature through said switch, and an additional coil on said relay energized through said switching means, an accelerator controller for controlling the operation of said switch, and a braking con- BASCUM O. AUSTIN. 

